| Maize ear rot is a serious fungal disease occurring the late growth stage of maize around the world.Maize ear rot not only reduces the yield of maize but also causes mycotoxin contamination,which affects the quality of maize and threatens human and animal health.Fusarium verticillioides is the predominant causative pathogen of maize ear rot in China.At present,there is no registered fungicide for use against maize ear rot in China.The novel isopropyl alcohol-triazole fungicide mefentrifluconazole(MFZ)has lower embryo fetal toxicity and teratogenicity than other triazole fungicides,and has good antibacterial activity against various plant pathogenic fungi,but its antibacterial activity against F.verticillioides has not been reported.In order to determine the potential application of MFZ against maize ear rot,the effects of MFZ on the mycelial growth,conidial production,germination and germ tube elongation of 50 F.verticillioides strains collected from Shandong,Henan and Jiangsu provinces in China from 2019 to 2021 were determined by mycelial growth rate and conidial germination method,respectively.The effects of MFZ on B-type fumonisins(FBs)production and the expression levels of FBs biosynthesis genes of F.verticillioides were determined.The mechanism of action was explored by measuring relative gene expression levels,the production of ergosterol,glycerol,malondialdehyde(MDA)and mycelial conductivity of F.verticillioides after MFZ treatment.Finally,MFZ and its compounding agent were applied to the field to evaluate their control effect on maize ear rot.The results showed that:1.MFZ had strong antifungal activity against 50 strains of F.verticillioides,and had a dose-dependent inhibitory effect on mycelial growth,conidial production,germination and germ tube elongation of F.verticillioides.The EC50 values of MFZ inhibiting mycelial growth of F.verticillioides ranged from 0.013 to 0.091 μg/mL,with an average EC50 value of(0.041±0.017)μg/mL.The average inhibition rates of EC50 concentration of MFZ on conidial formation,germination and germ tube elongation of F.verticillioides were(19.17±4.12)%,(19.12±4.64)%and(33.29±4.94)%,respectively.MFZ reduced the production of FBs and the expression level of FBs biosynthetic genes significantly,and the inhibition rate of FBs production was 34.48%.2.The expression levels of 2575 genes were in the genome of F.verticillioides significantly changed after treated with MFZ at EC50 concentration.These genes were mainly involved in redox biological processes,steroid biosynthesis pathways and MAPK signaling pathways.The production of ergosterol in mycelia of F.verticillioides was significantly reduced by 41.08%,and the expression level of CYP51B(fungicide target encoding gene)involved in ergosterol biosynthesis was up-regulated by 7.36 times.At the same time,the production of glycerol,MDA and relative conductivity were increased,and the induction rates of glycerol and MDA were 94.28%and 22.49%,respectively.3.A 2-year field experiment showed a significant reduction in ear rot severity in maize after spraying with MFZ at the tasseling stage.Field experiments showed that the control effects of 150,225 and 300 a.i./(g/hm2)MFZ 20%SC and 150 a.i./(g/hm2)MFZ+metconazole(1:2)20%SC against maize ear rot were(15.12±5.67)%,(20.93±5.16)%,(30.23±6.97)%and(24.75±4.42)%,the yield increase rates were(5.70±1.58)%,(9.96±1.36)%,(11.45±2.69)%and(10.35±2.07)%,and the inhibition of FBs levels were(33.67±5.15)%,(46.78±3.51)%,(53.14±4.88)%and(47.75±5.23)%,respectively,which were better than the control fungicide prothioconazole+tebuconazole(1:1)40%SC in 2021.The data trend in 2022 was basically consistent with that in 2021. |
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